The instant invention relates to control circuitry for a vehicle passenger safety restraint, such as an air bag, seat-belt tensioner, adjustable knee bolster, etc., which includes means for sensing the presence, size, and position of vehicle passengers for the purposes of 1) warning a passenger in the event that he assumes a position within the vehicle likely to significantly reduce the effectiveness of the restraint should it become necessary to subsequently actuate or deploy the restraint, e.g., in the event of a vehicle collision or marked vehicle deceleration; 2) inhibiting operation of the restraint in the event that such restraint operation is likely to cause greater injury to the passenger than might otherwise result from unimpeded passenger contact with fixed interior structures of the vehicle; 3) corroborating vehicle acceleration data generated by other sensors, such as inertia-type crash sensors and/or frangible crush sensors located in the longitudinal crush zones of the vehicle, by observing changes in the sensed positions of the passenger over time; and, most preferably, 4) adjusting the response level of the restraint so as to provide maximum protection for the passenger upon ultimate deployment thereof, given the size of the passenger and his assumed position within the vehicle.
It is well known that the size and relative position of each passenger within a motor vehicle at the instant preceding a collision or marked vehicle deceleration is of critical importance to the effectiveness of safety restraints such as air bags in preventing serious injury. Specifically, known safety restraints operate to slowly decelerate each passenger relative to fixed interior structures of the vehicle, such as its steering wheel, dashboard, knee bolsters, etc., in order to avoid the high loads which would otherwise result from unimpeded contact of the passenger therewith. The size and position of each passenger within the vehicle at the instant before the operation of the restraint are thus critical in determining the rate at which the passenger must be decelerated relative to such fixed interior structures by the restraint in order top prevent such injurious contact therewith. The relationship between passenger size and position, and proper operation of the restraint becomes even more critical when the restraint is deployed from one such fixed interior structure, as where an air bag is deployed from the steering wheel hub or a dashboard compartment, and the passenger leans towards or otherwise assumes a position proximate thereto, thereby requiring a higher rate of passenger deceleration in order to prevent deleterious contact between the passenger and the vehicle's fixed interior structures.
Additionally, under certain circumstances known to one skilled in the art, such as in the "standing child" scenario, the injury likely to be suffered by an "out-of-position" passenger as a result of the deployment of the restraint may well exceed the injury which might otherwise result from unimpeded passenger contact with fixed interior structures. In such cases, the operation of the restraint is preferably inhibited.
The prior art has heretofore failed to provide a means for indicating to a vehicle passenger the fact that he has assumed a position within the vehicle likely to reduce the effectiveness of a safety restraint and, hence, likely to result in greater injury should operation of the restraint be subsequently required. In other words, under the prior art, an out-of-position passenger has not been afforded the opportunity to reposition himself within the vehicle so that he might be maximally protected against injury in the event of a subsequent crash or marked vehicle deceleration. Rather, the prior art approach has focussed on simply reminding the passenger to use "active" restraints, such as manual seat-belts, as through the use a seat switch which closes to complete a portion of a warning circuit, whereby a visual or audible warning is generated in the event that a second switch in the belt's latching mechanism has not been closed.
The prior art has also sought to match the response of a safety restraint such as an air bag to the sensed rate of vehicle deceleration. Specifically, the prior art teaches the use of air bag inflator assemblies comprising a plurality of individually-triggerable gas-generating cartridges, which cartridges are selectively triggered based upon the rate of vehicle deceleration sensed by at least one inertial sensor. This approach fails, however, to adjust safety restraint response to account for passenger size or position; and there is no accommodation of situations such as that of the "standing child", where operation of the restraint is preferably inhibited.
Alternatively, the prior art has adjusted the threshold vehicle deceleration that is required for triggering operation of one restraint in response to the detected use of another passenger restraint employed within the vehicle. For example, U.S. Pat. No. 4,804,859 to Swart teaches a trigger circuit for an air bag whose firing path incorporates one of a pair of crash sensors having different acceleration thresholds based upon passenger seat-belt usage. Thus, where the passenger fails to utilize his seat belt, the lower-threshold crash sensor will be employed to trigger the deployment of the air bag upon sensing an acceleration exceeding its threshold value. Significantly, the triggered response of the air bag safety restraint taught by Swart remains the same, regardless of seat-belt usage; the passenger is not warned, for example, of the reduced likely effectiveness of both his seat-belt and the air bag as he leans forward to adjust a knob on the dashboard; and, once again, there is no accommodation of the "standing child" and other like scenarios.